In any data transmission scheme it generally desirable to send data from a source to a destination as quickly as possible. However, it is also generally necessary to send a certain amount of overhead information along with the data in order that the transmitted data will be successfully received and processed.
The overhead information may tell a destination device how to acquire an incoming signal; it might identify what kind of a signal is being sent; it might tell a destination device how much data is being sent or in what format the data is being sent in, or the like. But while this information is important, it is not the same as the underlying data to be sent. And time spent sending overhead information is time that is not spent sending data. Thus, the greater the amount of overhead data that is associated with a given set of transmission data, the lower the transmission throughput of that data will be.
However, the overhead data serves a real purpose, namely to facilitate the transfer and successful receipt of the data. And so if the overhead information is reduced in size too much, then it may fail in this purpose and the data transfer might fail. This would also cause the data transmission speed to be reduced since it would require certain sets of data must be retransmitted.
It is therefore desirable to reduce the amount of overhead information that is used for a given amount of transmission data, without significantly increasing the chance that a particular data transmission will fail, and minimizing the necessary measures to correct any errors that do occur.
Furthermore, some systems will use an acknowledgement mechanism whereby successful receipt of data sent from a source device to a destination device will be acknowledged by a return transmission including acknowledgment information from the destination device back to the source device. In this case, the acknowledgement information provides a valuable indication regarding whether data was successfully received, but also takes up channel time that could otherwise be used for data transmission.
Thus, when an active acknowledgement policy is used, it is desirable to minimize the amount of channel time used to achieve successful signal acknowledgement.